Launched in August 1962, Mariner 2 performed a carefully calculated engine burn on its way to Venus, fine-tuning a trajectory that would carry it past the planet in December. The maneuver, among the first of its kind, proved that spacecraft could be steered across millions of miles of empty space toward a precise rendezvous with another world.
Mariner 2's mid-course correction on September 4, 1962, was a quiet but pivotal moment in the young space age. Ground controllers, working with computing power that seems laughably primitive today, calculated a small rocket burn designed to nudge the spacecraft's trajectory just enough to intercept Venus more than two months later, after a journey of some 180 million miles.
The stakes were enormous. Mariner 1, its predecessor, had been destroyed by a range safety officer just minutes after launch in July 1962 due to a software error, famously traced to a missing hyphen in the guidance code. Mariner 2 carried the hopes of the entire Venus program, and NASA's credibility in interplanetary exploration, on its shoulders.
The correction succeeded, and on December 14, 1962, Mariner 2 became the first spacecraft to fly past another planet, passing within about 21,600 miles of Venus and radioing back data that dispelled fantasies of a lush, habitable world, revealing instead a hellish surface baking at some 800 degrees Fahrenheit beneath thick clouds. The October course correction demonstrated for the first time that humans could reliably steer a machine across the solar system, a technique that underpins every deep-space mission since.